So it appears that the tracks, if purchased directly from Apple today, are indeed DRM-free. But the songs included as part of the free compilation are older versions that are otherwise invisible to prying eyes on the iTunes Store.
Is this a reversal of Apple's stated DRM-free policy, or just some kind of quirky loophole Apple keeps open for those who want to give away free songs on iTunes? I attempted to contact Apple for clarification, but had not heard back at the time this story was published. Either way, it's been a long time since I've seen a new DRMed track appear in my iTunes library.